You can make a nandroid backup to be sure with streakmod recovery,
you have to put the file (previously nammed update.pkg) on your SD card,
You have to change your recovery to 350, and reboot on recovery to restaure the update.pkg.
You have to wait.... a litlle bit....

Mine is an unlocked Canadian and it rocks
just when you have to click on the droid, click on the bottom right button to change the language to english

Ah well, i have a Note now, so i think i can be a bit more daring with the Streak . .
Maybe next i'll try Streakdroid . . And i will absolutely try, when DJ Steve makes good on his word to try and get ICS on the Streak5 . .

Edit:
And nope, Update does not work. Errors out and reboots into normal 2.2.2

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